Children or young adults with heart problems sometimes cannot be fixed with surgery. This may result in many symptoms and occasionally the need for heart transplantation. Labetalol may improve symptoms and potentially reduce the need for heart transplantation. In order to participate in this study participants will be screened to ensure that they meet certain criteria: stable congestive heart failure as a result of decreased cardiac function. Study subjects will undergo physical examination and have an ECG, echocardiogram, exercise test, and have 2-3 teaspoons of blood drawn for testing. Labetalol will be administered in the clinic on successive weeks until maintenance dosage has been established. Subjects will undergo repeat ECG, echocardiogram, and exercise testing after maintenance dosage has been determined, and again after 6 months of maintenance therapy. At the 6 month visit, 2-3 teaspoons of blood will be drawn. Subjects will also be seen in clinic after 2 and 4 months of maintenance therapy for physical examination and assessment of tolerability. Labetalol therapy will then be discontinued slowly. Participants will undergo repeat ECG, echocardiogram, and exercise testing a final time 2 weeks after labetalol therapy has been discontinued. subjects will be seen in clinic approximately 8-10 times during the course of their involvement in this study. Potential side effects from labetalol include low blood pressure, slow or irregular heart rate, drowsiness, dizziness, fatigue, behavioral changes, headache, rash, nausea, vomiting, dry mouth, sexual dysfunction, urinary problems, nasal congestion, and bronchospasm. However, most adverse effects of labetalol are mild, transient, occur early in therapy, and may be avoided by a slow increase in the dosage. Extensive testing will be provided to participants as part of this study at no cost to subjects or their insurance providers. Labetalol will also be provided at no cost. If the study medication has the expected effects, participants may experience a decrease in symptoms and improved cardiac function. The results of this research will provide information needed to develop new ways to treat chronic congestive heart failure in the future. Medical science, children, and society in general can be expected to benefit from this study.